Over the past decade, Bone Marrow Transplantation (BMT) has evolved from an experimental procedure reserved for patients with refractory leukemia into a rapidly expanding area of clinical investigation that offers high cure rates for patients with aplastic anemia, acute and chronic leukemia, and selected types of lymphoma. The objective of BMT is to provide a healthy stem cell population that will differentiate into blood cells to replace deficient or pathologic cells of the host.
There currently exist two generally accepted procedures for bone marrow transplantation. The first and most common procedure is allogenic bone marrow transplantation in which bone marrow is obtained by aspiration from the iliac crests of an HLA-compatible donor and infused into the patient requiring the healthy hematopoietic marrow. The procedure in which the bone marrow is aspirated through a puncture site into the iliac crest is very painful to the donor and sometimes obtains limited quantities of useful, transplantable hematopoietic tissue.
The second option for BMT involves autologous transplantation (ABMT); namely removal of a patient's own marrow for safe keeping when the patient is free of disease or when a complete remission has been induced by radiation and chemotherapy, or by other therapeutic means, followed by ablative treatment of the patient with the hope of destruction of any residual tumor and rescue with the patient's own bone marrow. Since an autograft is used, no immunosuppression is necessary and graft versus host disease (graft rejection) is minimal. Because the autologous "rescued" bone marrow can produce mature blood cells quickly, ABMT allows patients to tolerate very high doses of chemotherapy with less risk of infection and bleeding. Nevertheless, the success of autologous BMT is strictly dependent on obtaining sufficient quantities of healthy bone marrow from the patient-host during a period of tumor remission and when healthy hematopoietic tissue is present and obtainable. Although ABMT has some therapeutic advantages, it remains a difficult, somewhat risky, and expensive procedure.
While graft versus host disease (implant rejection) and infections are both issues in BMT, the major limiting factor in the use of BMT is the availability of sufficient quantities of healthy, immunologically compatible bone marrow tissue with sufficient hematopoietic activity, which in turn results from a lack of suitable donors. Since only 25 to 30% of patients have a sibling who can serve as an HLA-compatible donor, alternatives need to be found.
Clearly, there exists a need to make the procedure for the retrieval of bone marrow for transplantation more accessible, less painful (i.e., avoid puncture of the iliac crest and the associated morbidity), increase the availability of useful bone marrow and bone marrow cells, and control more easily the microenvironment around the implant to enhance bone marrow formation while potentially removing or eliminating tumor cells and other undesirables in the bone marrow as well.